Definitely not cool using the memorial or other people's property without permission. I understand the logic of wanting to get your dog to do the same command in as many places as possible to proof the command. I'm okay with using things like benches, or that are part of a park's playground equipment, provided there are no kids around (you aren't going to accomplish much with kids there anyway). The people who use other people's property without permission, or memorials that other people have deep feelings for risk getting all dog owners banned from public locations. There are already so many places you can't take your dog, can only take them on a leash, etc. we don't need more restrictions placed on us due to thoughtless owners and trainers.